"Gain" from impedance matching transformer (?)

[keith.rogers]

From memory, the Shure 545's that had alternate impedances had a 4 pin Tuschel type connector and they enabled the selection of impedance. Mine had low on an XLR and high on a ¼"TS cables.I cannot remember if the XLR was balanced or unbalanced?

Yeah, that's the first 545 spec I found. You have to re-wire or re-cable (with the correct kind of cable) to actually change the impedance. Those [high-impedance usages] were almost certainly intended for use with the old screw-on connector at the mixer end.

https://pubs.shure.com/guide/545-S/en-US

Even the later 545SD requires changing the internal wiring, as shown in the spec link I posted earlier.

OP never said he'd been changing wiring to go from low to high impedance, or which 545, so some guessing going on.

 

[CoolCat]

the current 545 have a little jumper that changes it from Low Z to High Z on the XLR. You dont need solder or anything. OPen it flip the little plug.

545 works great in Low Z as any sm57.

With internal High Z setting it seems a waste of time and makes sense why they stopped having hiZ in the SM57.
As Keith posted maybe need a cable for it in High Z 545? or the A85F plug....I guess its for people talking in a Bingo Parlor PA or a thru a guitar amp.
imo the HiZ stuff is a waste of time and the HiZ plugs A58F are too..... I dont have any use for them.

The resistor on a XLR, LOWER-Z tool...changes it to 600ohm for a typical interface or preamp(1k-3k).. is more interesting, but thats another thread maybe?
ADD: the LOWER Z thing showed up, nice and easy to plug in, well worth money,...it has a resistor soldered in the xlr to XLR barrel, no transformer. Simple.
I hear a difference and with the 600ohm it smooths the 545 a bit, for me I like it better...
545 lowZ into a 1400ohm interface mic pre vs 545 lowz into the LOWER-Z 600ohm to the 1400ohm interface preamp.
the 600ohm resistor takes some peeky-mid spike out of the sound, smooths it subtly in a good way. imo